The picture of the Observation / Gun Platform on One Tree Hill is in a wooded area and close to the once iron railined enclosed Honour Oak Tree.
These would all be a danger to a Balloon with a crew cabin hanging below it and coming into contact with a fabric covered wooden frame.
That site has nothing to do with the Zeppelin anchorage base on Furze Hill backing onto Hornimans Gardens.
Here the conrete blocks with iron rings were below ground level giving no obstruction to a balloon that might be uncontrollable in high winds to bring down safely and secure.